1. Field of the Invention
The present invention relates to a disk control system and method, and in particular, to a disk control system and method that continuously writes write-requested data to a stripe on a disk using only a main memory and a disk apparatus and without using any exclusive non-volatile memory constituting a write buffer and an address mapping table and which is conventionally used for a RAID control device.
2. Description of the Related Art
A method of writing all data to a physical stripe as one continuous area of random writes as shown, for example, in Jpn. Pat. Appln. KOKAI Publication No. 6-214720 and Jpn. Pat. Appln. KOKAI Publication No. 11-53235 has been proposed as a write method for a disk control system of a RAID configuration. In the prior art, however, write data are written to a nonvolatile memory (hereinafter referred to as an “NvRAM”) or a volatile memory, and once write data amounting to one stripe have been provided, they are written to the physical stripe on the disk apparatus. Further, the NvRAM stores an address mapping table in which logical addresses from an upper file system are translated into physical addresses on the disk.
When the data are thus written to the NvRAM, even if the system is shut down before the data are written to the disk apparatus, the write can be completed by referencing the NvRAM after system reboot and correctly writing the data in the NvRAM which have not been written yet, to the disk apparatus (no write data are lost).
That is, as long as the data write to the NvRAM has been completed, no write data are lost. Thus, once the write data have been written to the NvRAM, the conventional disk control apparatus notifies, in response to the write request, the host that the write has been “completed”.
The NvRAM, however, must be provided in an I/O card (hardware) installed in the system, thus disadvantageously requiring corresponding costs. Other problems include the compatibility of the system with a host computer or other equipment, the needs for maintenance, and the like.